After washing a gas turbine engine, waste and moisture are removed from the engine via drain valves. At normal operation it is essential that these drain valves remain closed.
Drain valves are used to drain oil, moisture or water from a gas turbine engine after a washing procedure. Usually, drain valves are actuated by a supply of compressor air. If the air supply line was interrupted while the gas turbine engine is in operation, the drain valves could open and the hot gases at high pressures would enter potentially flammable drain tanks.